In precision sand casting processes for forming a casting, such as for an internal combustion engine block, an expendable mold package is assembled from resin-bonded sand cores. The sand cores define the internal and external surfaces of the casting. Resin-coated foundry sand is generally blown into a core box and cured to form the expendable mold package. A typical mold package is shown and described in commonly owned U.S. Pat. No. 6,615,901, the disclosure of which is incorporated herein by reference in its entirety.
Following the pouring of molten metal such as aluminum or cast iron to form a casting, the sand cores must be removed in a process known as “decoring”. A decoring machine is generally employed to remove the sand core material from the casting. The casting is typically pre-processed prior to loading the casting into the decoring machine. Pre-processing may include a high energy impacting of the casting, for example, using pneumatic hammers and the like. The impacting fractures the internal cores, allowing at least a limited amount of core movement inside internal passages of the casting. The decoring machine exploits the limited core movement to cause a further breakdown of the core into flowable sand.
A typical decoring machine may employ the shaking principle for further pulverizing the sand core and transporting the core material outwardly from the decoring machine. A known decoring machine employing the shaking principle is the Swingmaster™ decoring machine, manufactured by Fill Gesellschaft m.b.H. in Austria and distributed in North America by Rimrock Corporation in Columbus, Ohio. The Swingmaster™ decoring machine is described in Austrian Patent No. 003791, hereby incorporated herein by reference in its entirety. The Swingmaster™ decoring machine has two unbalanced type shafts that create a direct force in the direction of the swing that results in a sinusoidal vibration of the casting. The Swingmaster™ decoring machine removes cores from the casting by subjecting the casting to sinusoidal vibration of sufficient amplitude, and simultaneously rotating the casting about a horizontal axis, to break down the core. The rotation of the casting about the horizontal axis by the decoring machine may further allow free-flowing sand and core material to fall from the internal passages of the casting. The remaining core material is allowed to move more freely within the passages upon removal of the free-flowing sand and core material, hastening the pulverization and eventual removal of the core from the casting. A significant amount of the core can thereby be broken down and removed from the internal passages of the casting.
The typical decoring machine and process do not remove individual sand grains that may adhere to the casting wall due to phenomena known as “metal penetration” and “burn on”. The removal of the adhered material in the internal passages of complex castings is typically accomplished by subsequent processing. The removal of the adhered material may be accomplished by at least one of: surface impact means such as shot blasting and the like; abrasive means such as grinding, vibratory media cleaning, brushing, chiseling and the like, erosive means such as high velocity water jet and the like; and high energy mechanical shock such as electric arc/water-submerged processing and the like. Each of these methods undesirably adds to the cost and complexity of the decoring process.
There is a continuing need for a cost-effective method and system to remove core sand and other contaminants from narrow passages in aluminum and cast iron castings. Desirably, the method and system maximize the reliability of cleaning complex castings.